Containers for storing fluids have generally been of the disposible type but recently greater emphasis has arisen concerning the reuse of such containers. Reuse of the container is particularly desirable where the container is large and represents a substantial investment in its initial cost. Generally, such containers must be cleaned before reuse to avoid contamination by the coating and/or residuals left in the emptied container from its previous use. The inside of the container may be coated with an inert material which will not react with the material to be contained and can have a characteristic which would tend to militate against the adherence by the contained material. Cleaning and coating of such containers is a nuisance and in many instances raises the cost to exceed the cost of a new container thereby justifying disposal of the old container and the purchase of a new container.
Attempts at an economical solution to permit the reuse of containers have included the use of disposable liners such as plastic bags. The bags are preferrably of a thin pliable wall to minimize space requirements and provide for easy manipulation upon removal.
An example of a container for liquids is a 55-gallon paint drum which can be equipped with a cover for sealing the top of the drum when the paint is transported and/or stored. The container cover may be replaced, when the paint is to be used, by a cover having an integrally mounted pump and agitator mounted thereon. The pump cover is removable for use on a plurality of drums. The pump on the pump cover is used to dispense the paint and the agitator is used to mix the paint. One of the problems associated with the use of disposable liners in general and with the above paint drum in particular is the collapse of the liner upon dispensing of the paint. In the closed drum with a dispensing pump, in particular, liner collapse can occur because of the vacuum produced in the drum by removal of the paint by the pump. The vacuum is desirable from the standpoint of preventing oxidation of the paint by air which would otherwise fill the space vacated by the paint.
The collapse of the liner results in the liner being pulled to the inlet of the pump where the impervious liner blocks the inlet upon contact with it and prevents the flow of paint.
Another problem is the tendency of the liner to shift within the drum when the drum is treated roughly in shipping, or when the paint is agitated or mixed, each of which can result in the tearing of the liner. Further, where air pockets have formed between the liner and the drum, particularly at the intersection of the bottom of the drum and the side walls, a shifting of the liner can cause movement of the air pockets whereby the liner is moved away from the drum toward the agitator and can be torn by the agitator upon contact therewith. The problem of shifting of the liner becomes even more acute as the level of liquid is lowered within the drum and the forces resulting on the liner from agitation and the vacuum within the drum are combined and act simultaneously on the liner.
Prior art liners having closed bottoms secured in a container have required assembly of a multiplicity of elements in the container while the liner is maintained in position. This labor increases the cost and reduces the advantage of container economy sought through use of a liner. It also is subject to faulty installation of the liner and ultimate failure of its intended function. Removal of the liner elements is complicated by such assemblies in that retainer elements both internal of the liner and external of the liner must often be separately removed to enable the liner to be removed, particularly where it is desired to avoid rupture of the liner and the contamination of the container by the residual liquids in the liner.
Liners installed in metal drums are prone to rupture during installation where they fit the container walls. Even if installed without mechanical perforation, with many of the fluids desired to be contained in reuseable containers having liners chemical penetration of the liners particularly at seams and bonded areas can be a problem. Thus mechanical protection of liners during their placement in a container and precautions against weakened seams or seams vulnerable to chemical attack are desirable.
The above problems are overcome by the present liner which militates against collapse of the liner while in use, entrapment of air between the liner and the container and shifting of the liner relative to the container by use of a specially adapted base for the liner which stabilizes the position of the liner relative to the container and prevents air pockets from forming between the liner and the container.
In a preferred embodiment of a liner according to this invention the liner is of unitary construction to facilitate installation in a container and removal therefrom once the liquid constrained from the container walls by the liner has been withdrawn. Seam construction and bonds to the pliant sheet material of the liner are arranged for maximum integrity against liquid leakage. This embodiment of a liner is provided with a bottom having such stiffness and collapse resistance as to be adapted to accommodate suction withdrawal and mechanical agitation of liquid contained thereby in the vicinity of the bottom without displacement into the agitator or the suction inlet.